G. Lullo

University of Palermo

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Gianpaolo Vitale

Institute for High Performance Computing and Networking

Daniele Scirè

University of Palermo

Ugo Lo Cicero

National Institute for Astrophysics

Marco Barbera

Osservatorio Astronomico di Palermo

A. Collura

Osservatorio Astronomico di Palermo

C. Arnone

University of Palermo

Roberto Macaluso

University of Palermo

Mauro Mosca

University of Palermo

Salvatore Varisco

Osservatorio Astronomico di Palermo

Luisa Sciortino

University of Palermo

Cooperative Institutions

University of Palermo

National Institute for Astrophysics

Osservatorio Astronomico di Palermo

Centre National de la Recherche Scientifique

National Research Council

STMicroelectronics (Italy)

University of Rome Tor Vergata

University of Palermo

University of Glasgow

Center for Astrophysics Harvard & Smithsonian

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RCE photodetectors based on VCSEL structures

IEEE Photonics Technology Letters (1999)

T. Knödl H.K.H. Choy Janet Pan R. King R. Jäger

We have fabricated top illuminated resonant cavity enhanced (RCE) detectors by partially removing top-mirror pairs of a vertical-cavity surface-emitting laser (VCSEL) structure by etching. The observed maximum quantum efficiency is 73% with a spectral full-width at half-maximum (FWHM) of about 1.7 nm. This particular RCE detector was fabricated by etching away 8 top-mirror pairs of a VCSEL structure, with 15.5 top-mirror pairs remaining. Spectral FWHMs as wide as 6.5 nm, with a peak efficiency of 36%, have been measured in the case of 4.5 top mirrors remaining. An increase in the 3-dB detector bandwidth up to 2.8 GHz is observed by reducing the active device diameter from 90 to 20 μm.

Vertical-cavity surface-emitting laser

Quantum Efficiency

Spectral width

10.1109/68.789720

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Citations (44)

Pulsed laser deposition of ZnO and VO2 films for memristor fabrication

Claudio Calì F. Di Quarto G. Lullo Roberto Macaluso Fulvio Caruso

Pulsed Laser Deposition

Deposition

Memristor

Source

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Experiments on chaotic circuits and crypted data transmission

G. Lombardo G. Lullo R. Zangara

The basic concepts of deterministic chaos have been recently included in several classes for undergraduate students, both in Engineering and Physics courses. An experimental approach proves effective in raising the learning rate for students who face for the first time these new concepts. In this paper we propose a versatile electronic circuit for chaos generation and observation, which can also be used in experiments on crypted data transmission.

10.1109/icecs.2001.957778

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Citations (1)

Quantum well intermixing with high spatial selectivity using a pulsed laser technique

Electronics Letters (1995)

C.J. McLean Andrew McKee G. Lullo A.C. Bryce R.M. De La Rue

The authors demonstrate a new quantum well intermixing technique which allows bandgap shifts of typically 100 meV to be realised with a high spatial resolution in a GaInAs/GaInAsP MQW waveguide structure. The material was irradiated with pulses from a Q-switched Nd:YAG laser, and was then subjected to rapid thermal annealing at 700°C for several minutes. The spatial resolution of the disordering process was investigated across a masked interface, and was determined to be ≤25 µm.

Integrated Optics

10.1049/el:19950868

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Citations (29)

Influence of electrodes layout on hydrothermally-grown GaN/ZnO LEDs

Mauro Mosca D. Caltagirone G. Lullo Roberto Macaluso Corrado Calì

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Low temperature solid-source molecular-beam epitaxy growth of Al-free quantum well laser diodes using a GaP-decomposition source

Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures Processing Measurement and Phenomena (1999)

P. A. Postigo G. Lullo K. H. Choy Clifton G. Fonstad

Low threshold aluminum-free, InGaP/GaAs/InGaAs quantum well laser diodes have been grown at low temperature on GaAs using a GaP sublimation source for phosphorous and an atomic hydrogen cracker source for substrate surface preparation. The growth cycle was conducted entirely below 470 °C so that it is compatible with growth on GaAs very large scale integrated circuits, as in the epitaxy-on-electronics monolithic optoelectronic integration processes. The room temperature pulsed threshold current density of broad-area stripe contact laser diodes was consistently on the order of 0.38 kA/cm2. InGaP grown with the GaP cell is found by secondary ion mass spectroscopy to contain significant amounts of oxygen, particularly in Be- and Si-doped layers.

Sublimation

10.1116/1.590740

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Citations (9)

Chemical Bath Deposition as a Simple Way to Grow Isolated and Coalesced ZnO Nanorods for Light-Emitting Diodes Fabrication

2018 IEEE 4th International Forum on Research and Technology for Society and Industry (RTSI) (2018)

Mauro Mosca I. Crupi Daniele Carmelo Russotto G. Lullo Roberto Macaluso

A way to grow and characterize isolated and coalesced ZnO nanorods on p-GaN/sapphire structure is presented. Chemical bath deposition can be used to grow ZnO nanorods of device-quality, simply controlling the duration time of the growth process and the concentration of the nutrient solution in the bath. Increasing the duration of the process, as well as the concentration of the solution, leads to compact and sound layers instead of separated nanorods. However, too high concentrations stop the growth process. Light-emitting diodes fabricated on these ZnO-p-GaN heterostructure have a peak of electroluminescence at 400 nm and exhibit interesting electrical and optical properties. Optical power of 225 μW at 0.425 A/cm ² and a related wall-plug efficiency of 0.23% are obtained with 2 mm-diameter LEDs fabricated on a ZnO layer grown for 30 h in a solution of concentration 70 mM. The performances shown by these LEDs can be used as a way to test the quality of the ZnO growth.

Nanorod

Chemical bath deposition

Solution process

Deposition

10.1109/rtsi.2018.8548374

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Citations (2)

A Measurement System for Power Inductors in Non-Linear Operating Conditions

Marco Ventimiglia Daniele Scirè G. Lullo Gianpaolo Vitale

The exploitation of power inductors in switching converters outside the linear region requires detailed information on the magnetization curve that often is not included among those usually available on their datasheets. This paper proposes an automatic system in which the inductor is characterized in real operating conditions taking into account also the core temperature. It is based on a switching converter suitably controlled by a virtual instrument. The system was tested by retrieving the inductance vs current curves of two commercial inductors for core temperatures up to 105°C, showing the different behaviors of the magnetization curves. Results are coherent with data given by manufacturers and provide a complete characterization of the inductors.

10.1109/isie45552.2021.9576289

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Assessment of MOSFET switching losses in an LLC converter by a calorimetric method

2022 IEEE Applied Power Electronics Conference and Exposition (APEC) (2023)

Alfio Scuto Giuseppe Sorrentino Marco Ventimiglia G. Belverde Domenico Nardo

The present work aims to implement a calorimetric method to measure the power dissipated during MOSFET switching in a high efficiency LLC resonant converter. The power dissipated from switching can significantly impact the total power dissipated by the device and consequent efficiency, so correct quantification is fundamental for optimizing the devices and increasing the efficiency of the converters. In LLC converters, this type of dissipated power cannot be measured with standard methods such as measurement with oscilloscopes as some of the energy that is recovered and not dissipated. The calorimetric method requires reasonably accurate measurement of thermal resistance and the temperature of the die. To facilitate accurate temperature measurement, we used a device in an ACEPACK™ SMIT package module, which incorporates a complete half-bridge and an NTC thermistor for reading the temperature.

Thermistor

Power MOSFET

10.1109/apec43580.2023.10131330

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Citations (1)

Manufacturing an active X-ray mirror prototype in thin glass

Journal of Synchrotron Radiation (2015)

Daniele Spiga Marco Barbera A. Collura S. Basso Roberto Candia

Adjustable mirrors equipped with piezo actuators are commonly used at synchrotron and free-electron laser (FEL) beamlines, in order to optimize their focusing properties and sometimes to shape the intensity distribution of the focal spot with the desired profile. Unlike them, X-ray mirrors for astronomy are much thinner in order to enable nesting and reduce the areal mass, and the application of piezo actuators acting normally to the surface appears much more difficult. There remains the possibility to correct the deformations using thin patches that exert a tangential strain on the rear side of the mirror: some research groups are already at work on this approach. The technique reported here relies on actively integrating thin glass foils with commercial piezoceramic patches, fed by voltages driven by the feedback provided by X-rays, while the tension signals are carried by electrodes on the back of the mirror, obtained by photolithography. Finally, the shape detection and the consequent voltage signal to be provided to the piezoelectric array will be determined by X-ray illumination in an intra-focal setup at the XACT facility. In this work, the manufacturing steps for obtaining a first active mirror prototype are described.

SIGNAL (programming language)

Active optics

Deformable Mirror

10.1107/s1600577515017142

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Citations (8)